Global kinetic modeling of the intrabinary shock in spider pulsars

在最迷人的天体物理对象中，“蜘蛛脉冲星”是一种特殊类型的快速旋转，在双星系统中非常紧凑的中子星。蜘蛛脉冲星被归类为红背星（RBs）或黑寡妇星（BWs），它们与一颗低质量恒星伴星在紧密的双星轨道上运行。脉冲星散发出强烈的相对论风。当影响伴星时，风加剧了伴星的烧蚀和质量损失，然后被脉冲星风“吞噬”——因此，这些系统的名字令人回味。哥伦比亚大学的一个研究小组将使用最先进的计算机模拟来更好地了解蜘蛛脉冲星和天体物理冲击波。首席研究员还将设计一门新课程，“简单的物理学、天文学及其他”，向哥伦比亚桥大学博士学者项目的学生介绍用定量的眼光看待现实的艺术，利用个人经验和先验知识作为指导，得出数量级的结论，从而准备好做出基于定量推理的决定。相对论脉冲星风由磁场极性相反的环形条纹组成，由热等离子体的电流片隔开。在强烈的冲击中，脉冲星风的冲击压力被伴星风或其磁层所平衡。双星内激波可能是粒子加速的有效场所，这就解释了为什么蜘蛛脉冲星的x射线和伽马射线光曲线经常在轨道周期上被调制。因此，对BWs和RBs的仔细研究可以帮助揭示毫秒脉冲星中脉冲星风的大部分未知物理特性，并有助于理解从波因廷通量主导到粒子主导的转变发生在哪里。该项目将涉及蜘蛛脉冲星内星胞内粒子动力学的第一性原理模拟，因此可以同时捕获磁场耗散、粒子加速和随后发射的微观物理，以及激波的整体形态和曲率以及由此产生的宏观流动动力学。虽然主要关注的是蜘蛛脉冲星，但磁主导的条纹激波中的粒子加速问题与其他系统中波印廷通量主导的相对论性流出的物理学有着深刻的关联，比如活动星系核的喷流和伽马射线爆发。这个奖项推进了“宇宙大创意之窗”的目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Among the most fascinating astrophysical objects are the “spider pulsars,” which are a particular type of very rapidly-rotating, extremely compact neutron stars in a binary system. Spider pulsars, which are classified as either Redbacks (RBs) or Black Widows (BWs), are in tight binary orbits with a low-mass stellar companion. The pulsar emanates an intense relativistic wind. When impacting on the companion star, the wind exacerbates ablation and mass loss of the companion, which is then “devoured” by the pulsar wind --- hence, the evocative name of these systems. A research team at Columbia University will use state-of-the-art computer simulations to better understand spider pulsars, and astrophysical shock waves in general. The lead researcher will also design a new course, “Back-of-the-envelope physics, astronomy, and beyond," to introduce students in the Columbia Bridge to Ph.D. scholars program to the art of looking at reality with quantitative eyes, using personal experience and prior knowledge as a guide to drawing order-of-magnitude conclusions, and thus to being prepared to make decisions that are grounded in quantitative reasoning.The relativistic pulsar wind consists of toroidal stripes of opposite magnetic field polarity, separated by current sheets of hot plasma. The wind terminates in a strong shock, where the ram pressure of the pulsar wind is balanced by the companion wind or its magnetosphere. The intrabinary shock may be an efficient site of particle acceleration, which would then explain why X-ray and gamma-ray lightcurves of spider pulsars are often modulated on the orbital period. Therefore, the scrutiny of BWs and RBs can help uncover the largely unknown physics of pulsar winds in millisecond pulsars, and aid in understanding where the transition occurs from a Poynting flux-dominated to a particle-dominated flow. This project will involve first-principles global kinetic Particle-In-Cell simulations of the intrabinary shock in spider pulsars, so one can simultaneously capture the microscopic physics of magnetic field dissipation, particle acceleration and ensuing emission, as well as the global morphology and curvature of the shock and the resulting macroscopic flow dynamics. While the main focus is on spider pulsars, the question of particle acceleration in magnetically-dominated striped shocks is of profound relevance to the physics of Poynting-flux-dominated relativistic outflows in other systems, like jets of active galactic nuclei and gamma-ray bursts. This award advances the goals of the Windows on the Universe Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.